Restructure of Guides section

The restructure of the Guides section is completed. The pages are now sorted under their process area (Requirements, Architecture, etc.) instead of their type (How to Guide, Reference Guide, etc.).

The changes also include:

• Create new folders and move markdown guides to the right folder.
• Update of links from other pages to the guides which have been moved.
• Update the taxonomy on pages (categories, tags, and roles).
• Spell, grammar, and markdownlint corrections.
• Automatically generate "related" links on process pages.

If you see any issues, please create a Process Change Request (PCR).